Alternating-current motor.



Patented July 4 1916.

B. G. LAMME.

ALTERNATING CURRENT MOTOR.

APPLICATION FILED JAN.26,1910- INVENTOR 56/7/4777/fl 6. [amine VATTORNEY WITNESSES UNITED STATES PATENT- QFFICE.

BENJAMIN G. LAMME, 0F PITTSBURGH, PENNSYLVANIA, ASSIGINOR r0WEsTINeHonsE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0EPENNSYLVANIA.

ALTERNATING-GURBENT MOTOR.

Specification of Letters Patent.

Patented Jul a, 1916.

To all whom it may concern: I

Be it known that I, BENJAMIN G. LAMME, a citizen of the United States,and a resident of Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement inAlternatingCurrent Motors, of which the following is a specification.

My invention relates to dynamo-electric machines and it has specialreference to alternating current motors of the commutator type.

The object of my invention is to provide a machine of the class aboveindicated that shall be relatively simple in construction and have thecharacteristics of a variable speed direct current shunt motor.

In Patent No. 839,935 granted to the Westinghouse Electric &Manufacturing Company, January 1, 1907, upon an application filed by me,is shown and described an alternating current motor of the com mutatortype which possesses the characteristics of a direct current shunt motorand in which the field of the motor is excited from one phase of apolyphase source of energy and the armature is supplied with currentwhich is displaced approximately 90 in phase from the field current.According to this arrangement, the armature is connected across atransformer by which the impressed voltagemay-be adjusted, the fieldremaining practically constant. A motor constructed in this way may bevaried in speed over a wide range by correspondingly ad usting thearmature supplyvoltage.

The principal disadvantage of a motor having the above indicatedstructure and circuit connections arises from the fact that preventiveleads or resistance connections are required in the armature winding inorder to reduce the short-circuit current at the brushes. Furthermore,it is diflicult to wind the armature for 100. volts or higher for use ona cycle circuit.

It is my aim to provide a motor which shall be capable of a speedvariation of approximately 5 and which shall be adapted for a frequencyof 60 cycles and for relatively'high-voltage circuits. I accomplish thisresult and obviate the. necessity for resistance leads byshort-circuiting the armature through the commutator brushes, as in amotor of the repulsion type, and by energizing the field or magnetizingwinding from one phase of a polyphase supplv circult and the primary orenergy winding from a different phase. The primary or energy winding andthe field or magnetizing winding are supplied with currents, whichdiffer in phase by substantially 90. The speed or the motor may bevaried bv vary mg the voltage supplied to the primary or energy windingbut, unless a very wide speed variation is required, I propose to varythe exciting current in the field or magnetizing winding by introducinga variable reactance or choke coil. By this means, the 90 phase relationbetween the two stator windings may be maintained, as is pointed out inmv previous patent to which reference has been made.

One of the principal advantages in the use of the motor of my presentinvention arises from the fact that the frequency in the armaturecircuit is low. under operating conditions, and, consequently,thecurrent which is short-circuited at the orushes may be held withinworking limits, since it is dependent upon the armature-currentfrequency. The armature may be wound for any suitable voltage andcurrent, irrespective of the supply voltage and, consequently, the motormav be adapted for operation on relatively high-voltage circuits. Whenthe motor is used on a two-phase circuit, the primary or energy windingwill, of course, be connected to one phase and the field or magnetizingwinding to the other phase of the circuit. If it is desired to operatethe motor on a threephase circuit, the usual arrangement of transformersfor changing from three-phase to two-phase may be emploved, but, inorder to avoid the necessity for this auxiliary apparatus, I propose toconnect the energy winding across two of the three-phase circuitconductors and to connect the field winding between the middle point ofthe energy winding and the third conductor. In other words, I establisha two-phase three-phase connection between the motor windings.

In the accompanying drawings, Figure 1 is a diagrammatic view showingthe circuit connections for a motor constructed in accordance with myinvention and Fig. 2 is a diagrammatic view of a developed statorwinding in which the distribution. of the energy and magnetizingwindings is such as to especially adapt the motor for use on three phasecircuits.

Referring to Fig. 1 of the drawings, the motor comprises an armature 1,a commutator cylinder 2, a primary or energy winding 3 and a field ormagnetizing winding 4. The commutator cylinder 3 is engaged by brushes 5and 6 which are short circuited by a conductor 7, the axis ofcommutation coinciding with-the axis of the primary or energy winding.The terminals 10 and 11 of the primary or energy winding are connectedto supply circuit conductors 12 and 13 which constitute one phase of thepolyphase source of energy. One terminal 14 of the field or magnetizingwinding 4 is connected to a supply circuit conductor 15 through avariable reactance coil 16, and

the other terminal 17 of the field winding 4 is connected to the supply"circuit conductor 18, when the motor is energized from a two-phasesource, or to the middle point 19 of the primary or energy winding 3,when the energy is received from a threephase source, a switch 20 beingarranged to interrupt the connection to the tap 19 when the motor isconnected to a two-phase circuit.

It is well known that a machine consisting of a stator provided withrectangularly disposed windings supplied from circuits with a 90 phaserelation and an armature provided with short circuited commutatorbrushes will operate as a motor of the repulsion type. With such anarran ement as described, one winding (the axis 0 whose field coincideswith the axis of commutation) is termed the primary or energy-windingwhile the other winding (the axis of whose field is displaced 90electrical degrees to the axis of commutation) is termed the field ormagnetizing winding.

In order that the exciting current which circulates in the two arts ofthe energy winding may not prodbce unbalancing or disturbing efiects,whenthe motor is supplied with energy from a three-phase source, it maybe found desirable to so distribute the energy winding that the twoparts are under'each ole of the motor. By this means, the exciting orfield currents which flow in opposite directions in the two parts of theenergy winding will neutralize each other. In Fig. 2 of the drawings,the two parts of the energy Winding are distributed as above indicated,the circuit connections being as follows :from the brush 21 of athree-phase generator 22,

through conductor 23 to coil 24; through coils 25 and 26, connector 27,coils 28, 29 and 30, connector 31, coils 32, 33 and 34, connector 35coils 36, 37 and 38 and conductor 39 to generator brush 40. The field ormagnetizing winding is connected, at one terminal, to brush 41 of thegenerator, circuit being completed from this point through conductor 42,coils 43, 44 and 45,

connector 46, coils'47, 48 and 49, connector 50, coils 51, 52 and 53,connector 54, coils 55, 56 and 57 and conductor 58 to the connector 31which joins the two halves of the energy winding.

It will be apparent from the foregoing statement respecting the flow ofcurrents in the respective portions of the windings, that the excitingcurrents from the connector 58 will flow in opposite directions in theconnector 31, and, consequently, will neutralize each other as regardscoils 24, 25, 26 and coils 32, 33, 34 and also as regards coils 28 29,30 and coils 36,- 37, 38.

I desire that my invention shall not be limited to the arrangement shownand described, and that modifications which do not depart from thespirit of my invention shall be included within its scope.

- I claim as my invention:

1. In an alternating-current motor, the

combination with an armature and a commutator having short-circuitedbrushes, of

a field or magnetizing winding, a primary or energy winding the axis ofwhich coincides with the axis of commutation of said brushes, oneterminal of the field or magnetizing winding being connected toanintermediate point in the primary or energy winding, in order to producea two-phase excitation in said windings when connected to a three-phasesourceof energy and a variable reactance in circuit with said field ormagnetizing winding.

2. In an alternating-current motor, the combination with an armature anda commutator having short-circuited brushes, of a field or magnetizingwinding, a primary or energy winding, the axis of which coincides withthe axis of commutation of said brushes, one terminal of the field ormagnetizing Winding being connected to an intermedlate point in theprimary or energy winding, in order to produce a two-phase excitation insaid windings when connected to a. three-phase source of energy, andmeans for adjusting the excitation of said field winding withoutaltering the phase relation between the currents in the said windmgs.

3. Inan alternating-current motor the combination with an armaturehaving shortcircuited brushes, of a primary or ener winding and a fieldor magnetizing win ing, one terminal of the field or magnetizing Windingbeing connected to an intermediate point in the primary or energywinding in order to produce a two-phase excitation in said windings whenconnected to a threephase source of energy, and each of the parts of thesaid primary or energy winding being so distributed as to be within theinfluence of each of the magnetic poles produced by the said field ormagnetizing winding.

4. In an alternating-current motor, the

combination with an armature having shortcircuited brushes, of a primaryor energy winding and a field or magnetizing winding, one terminal ofthe field or magnetizing winding being connected to an intermediatepoint on the primary or energy Winding in order to produce a two-phaseeX- citation in said windings when connected to a three-phase source ofenergy, and each of the parts of the primary or energy winding being sodistributed'that the magnetizing component of the current shall flow inop posite directions in adjacent parts of said winding.

5. In an alternating-current motor, the combination with an armaturehaving shortcircuited brushes, of a primary or energy winding and afield or magnetizing winding, one terminal of the field or magnetizingwinding being connected to an intermediate point on the primary orenergy winding in order to produce a two-phase excitation in saidwindings when connected to a three-phase source of energy and each ofthe parts of the rimary or energy winding being so distributed as toproduce a neutral magnetizing efi'ect.

In testimony whereof, I have hereunto subscribed my name this 19th dayof Jan,

BENJ. G. LAMME. "Witnesses:

E. LIVINGSTONE, B. B. HINEs.

